Activation of amylose



y 1965 F. J. GERMINO ETAL 3,184,335

ACTIVATION OF AMYLOSE Filed Dec. 29. 1960 ACYLATION ESTER SEPARATION WAT ER INVENTORS. FELIX J. GERMINO RAYMOND J. MOSHY 8 M 4 afm) ATTORNEY.

AMYLOSE BLENDER United States Patent 3,184,335 ACTIVATION 0F AMYLOSE Felix J. Germino, Peekskill, N.Y., and Raymond J. Moshy, Westport, Conn., assignors to American lJVIachine and Foundry (Iompany, a corporation of New ersey Filed Dec. 29, 1960, Ser. No. 79,427 13 Claims. (Cl. 12771) This invention relates to the activation of amylose for the purpose of enabling the derivatization of the activated product. More particularly, the present invention relates to the activation of amylose by partial disruption of the amylose hydrogen bonds brought about by swelling the amylose as distinguished from the activation methods in which amylose is solubilized.

Amylose, the linear fraction of starch, is obtainable commercially. With a few significant exceptions, it has chemical and physical similarity to cellulose. Amylose is a polyglucose linked by a-1,4 bonds and cellulose is a polyglucose linked by 61,4 bonds. This is the one notable chemical distinction between the two polymers. The 0: linkage, however, makes amylose digestible by amylase enzymes and thereby useful as a food ingredient, while the {3 linkage makes cellulose indigestible. The alpha configuration makes the glucose monomers of amylose spiral so that whole amylose polymer has a helical configuration. The cellulose polymer, on the other hand, is a linear rigid structure which is extensively hydrogen bonded and as a consequence is relatively much more insoluble than the amylose polymer. Commercial amylose is substantially insoluble in water. At normal pressure amylose is generally substantially insoluble in Water at any temperature i.e. generally less than 1% soluble. This is due to retrogradation of amylose, a condition in which amylose is a dense highly orientated or crystalline form. Retrograded amylose in the inactive or retrograded form has little utility. It is substantially insensitive to amylolysis and is water soluble. From a practical standpoint, it is chemically unreactive and requires extreme conditions, which usually cause molecular degradation, in order to effect chemical reaction to produce the derivative or useful form of amylose. Activated amylose, 0n the other hand, is capable of being derivatized under mild conditions with minimum degradation to form a variety of useful compounds.

Various techniques for preparing activated amylose have been attempted in the past. Insofar as known all prior techniques have been cumbersome, have substantially degraded the product and have been time consuming and impractical for producing activated amylose on any sizable scale.

The present invention provides a novel efficient continuous process which because of its process temperature and rapid activation precludes molecular degradation and/or bacterial spoilage of the amylose, a condition which has been a serious drawback in prior art procedures which employed long aqueous soak periods, e.g. in the order of 24 to 48 hours. The rapid process obviates the need for holding tanks and storage area thus substantially minimizing costs. Further, the invention provides an eflicient end product providing derivatives having an excellent degree of substitution.

It is accordingly an object of the present invention to provide an improved and practical method for the activation of amylose through the partial disruption of the ordered structure of retrograded amylose.

'It is a further object of the invention to provide activated amylose product economically in relatively high yields by a continuous process.

It is another object of the present invention to provide an improved method for obtaining derivatives of amylose.

It is still a further object of the invention to provide novel derivatives of amylose.

Additional objects and advantages of the invention will become apparent from the description of the invention hereinbelow.

In general this invention concerns the pretreatment of amylose for the purpose of activating this material. Activation being a practical requisite for chemical derivati- Zation of amylose. The extreme resistance of amylose is such that when chemical reaction of this material is forced, a serious degree of breakdown in the chemical links of the amylose polymer occur. As a consequence, amylose so degraded substantially loses its attractive properties, e.g. films prepared therefrom have a significantly decreased strength. Preferably the treatment of the amylose should be relatively mild in order that the molecular weight is not substantially diminished.

The essence of the present invention resides in the discovery that relatively brief treatment of amylose with water results in suitable activation whereas heretofore it was considered necessary that long periods of the order of 24 to 48 hours were required to effect activation. The activation by partial swelling of the amylose according to the invention is believed due to penetration through the non-reactive surface. According to the partial disruption, the penetration of water into the amylose is sufficiently effected within the first few hours of immersion of the dispersed amylose in Water. Further treatment is unnecessary and, in fact, prolonged soaking is a definite disadvantage, being accompanied generally by bacterial attack on the amylose.

The invention, in particular, concerns improved means to obtain activated amylose in relatively high yields, i.e. in the order of about and greater by using practically effective and efficient procedure. The method of the present invention disrupts the hydrogen-bonded structure in retrograded amylose by replacing glucose cross hydrogen bonds with glucose to water hydrogen bonds. The advantage of this method is that true solution does not occur. This avoids the complications encountered when starting from Water solutions of amylose. The activation by partial disruption according to the invention does not activat amylose in the same sense that amylose is activated by dissolution in water such as by autoclaving at high temperature and pressure as occurs when amylose is heated at about 160 C. under 90 psi. pressure. In the later case, amylose is in true solution and is completely hydrated. In the present case, the activation treatment does not cause solution but partially hydrates the amylose. In a sense, it causes small breaks or fissures in the retrograded structure which then allow the reactant to permeate the structure and more facile chemical reactions ensue.

By the process of the invention, amylose derivatives having a relatively high degree of substitution (DS) of about 3, which is maximum, are obtained. Degree of substitution contemplates the conversion of activated amylose such that the hydroxyl groups of each unit of the amylose molecule are substituted in the formation of the derivatives. Of the 3 available hydroxyl groups per glucose unit, i.e. a degree of substitution of 3, it is desirable that at least a degree of substitution of about 2.0 and preferably a degree of substitution close to 3 be obtained in the course of amylose derivatization. Derivatization of amylose is considered unsatisfactory from a practical standpoint in the case of acetate derivatives for example when of the product has a degree of substitution below about 1.5. With derivatives having longer chain lengths, i.e., having a chain length above about 4 carbon atoms, a degree of substitution somewhat this value may be appropriate.

The present invention provides a process whereby a -19 reactive form of amylose 'is'produced by partially disruptsolid v amylosev which provides "the 1 basis for the chemical.

change; i."e'.,lformationiof derivativesfromuhe activated" amylose.- In the absence of this treatment the amylose is relatively'inactive and non-productive of, derivatives;

'ing" the orderedstructure of retrograde' (unreactive)- and acylilchl'orides in .thepre'senceof asuitable catalyst.

lose ester to be derived. For example is the preparation of amyloseacetate; the final- Washpreferably containsglacial acetic acid.. Following-the final wash, the amylose now in activated stage is reacted at ,16p-by procedures known in the art to' form useful derivatives. In the preparation of esters-the activatedv amyloseis reacted with the appropriate-acylcompoundf such as acid anhydrides The followingexamples relatingto-the activation of amylose in solution further illustrate the invention and its advantagesl. x

Example 1:" A commercial amylose wasintroduced into a blender concurrently, with hot. water 95 1 00- C. at the rate of part'szotamyloseto ZOOparts of water. The holding time-"was '10 minutes. The aqueous slurry from the The procedure oftheiinvention' is illustrated by the single figure of the drawing" (depicting generally' the process of the invention)? in conjunction with the follow ing description.

Activation 'of' amylose according to the invention is efi'ectedby dispersing the amylosein an aqueous medium and'mixing for a period dependentonthe'temperature,

varying from about 0L5 minute to about 4 hours. Temperatures of from about room temperature C. to

about 100 C; may be employed; Lower temperatures may be used although no practical advantage is known for slowing the activation procedure by use'of temperatures below about 20 C. c As a general rule, conditionsin which temperatures ranging form about 25 C. to about 100 C. for periods ranging inversely from about B'h'ours to" about seconds, respectively, and depends .on the nature of the starting-amylose andthe degree of activation" desired. As shown in the flow diagram amylose andwater streams 1' and 2', respectively; are fed into the blender 3 where the amylose is} intimately di'spersedi Where retention periods. longer "than about 15 minutes are used, holding tanks (not shown) .may be employed In preparing theactiyatingsolutions,concentrations of amylose in the solvent as low'as 1% may be used. Preferably concentrations between about 3 and 23% are used but good results may be obtained with concentrations as high as about 25% at atmospheric pressure. At

higher solids contents the slurry-is .very viscous and.

presents some difiiculty inhandling; Most desirably concentrations of amylose between' abouti5 and.20% are employed. Water alone is a suitable dispersing activation medium for' th'e amylose althoughthe. addition of minor amountsof' organic liquids which are miscible with water and which do notsubstantially'dissolve amylose such as dirnethyl acetamide or methyl pyrrolidone are not precluded. The-dispersed amylose" is thereafter transferred,

as by pump '6and suitably separated by'any convenient means at'10"su'ch'as.by filtering,byidecanting or by cen-.

trifuging; Preferably the amylose is first precipitated by passage into a bath through line 7- comprising a suitable organic non-solventliquid which is miscible with water and in which the amylose is'in'soluble. As used herein,

7 the term precipitate is applied to thedehydration-ofQthat portion oftlie amylose which i swollen by the dispersing treatment. Organic non-solvent'liquids of'this type are known and readily characterizableas suitable by those.

sliillediin'the art. Included for example are glacial acetic acid, propionic acid, butyric.acid,.methanol, ethanol, pro- {film prepared therefrom Example 1..

blender. is thereafter precipitated by the introduction. thereof intoavmethanol bath where the aqueous slurry is thoroughly mixed. Holding time in the methanol bath is 3-4 minutes. Theprecipitated.amylose is separated from the. aqueous medium, washed once withmethanol andtwice with glacial acetic acid. The reactive amylose is readily-reactiveto-produce derivativein excellent yields.

Where reacted with acetic anhydride in the presence of sulfuric acid as catalyst,.a yield of"97.5% of amylose acetate is obtained. The product has a degree of substitution of--2.85". A film prepared from this-product dissolved in chloroform was clear andlustrous and had. a, tensilestrength of 6000 p.s.i. v

' Example 2 Commercially available amyloseisfedinto a blender concurrently with hot water (99 C.). at the rate of 20 parts of amyloseto 200 parts of water. :time after thoroughly blending the amylose in water The holding is onevminute.. The aqueous slurry from the holdingtanks is. fedintoa glacial acetic acid precipitating bath and thoroughlymixed. Holding time in-the acetic acid bath is 2' minutes. Where the solid portion ofthe amylose is precipitated, the amylose from the. precipitation step is separatedfrom thev aqueous medium by filtration and Washed twice with glacial acetic'acid. Amylose acetate is readily prepared from this activated amylose by aconventional. procedure.. Upon 1 reaction with aceticv anhydride sulfuric. acid as; catalyst, a-yield of 93% amylose acetate having a degree ofv substitution 2.6'is obtained. A was comparable to that of Example. 3

Commercially'available amass. is fed into a blenderconcurrently with water 22 C. at'the rate of 40 parts of amyloseto 250 partsof water. The holding time after thoroughly blending'the amylose in water is 2 hours.

The aqueous slurry from the holding tanks is fed" into a methanol precipitating bath and thoroughly, mixed.

. Holding timein' the methanol bath. is 2 minutes.v Where the solid' portion of the amylose is: precipitated,.the

panol, acetone, methyl ethyl ketone, dioxane andthe like.

Where the. precipitation step isus'ed fthe precipitated slurrywithdrawnat' 9 is then introduced into a suitable separation apparatus 10. wherethe amylose is-separated.

from the aqueousgorganic medium. The-separatedamylose is thereafter washed by ble'nding at 12 with-an or ganic' non-solvent liquid, separated at .13, given .a, final wash while blending at 14 withi'la non-reactive organic liquid and separated at'15; Preferably the final wash employs an acid having arcommonacyl-group the amyamylose'from the precipitation step is separated from the aqueous medium by filtration, and-washed three-times with glacial ,aceticiacid. Amylose acetate is readily prepared from. the'thus treated amylose by a conventional procedure; Upon reaction withacetic anhydride sulfuric.

acid as catalyst, the yield of 94% amyloseacetate'having a degree of substitution.3.0 is obtained, The product forms excellent films.. v

' Example 3(2) I The procedure of Example 3. is substantially repeated;

with the exceptionhthat the product washedwith glacial acetic acid is. reacted with-a mixture of acetic anhydride and butyric' anhydride in the ratio of 2.5 1 in the presence of sulfuric acid as catalyst. A yield of the-mixedester is derived having. a degree of substitution of 1.95 acetylgroups and 0.85 butyrl groups; Inalike manner a mixed ester of acetate and propionate as well as other combinations may be prepared by suitable reactions.

Example 4 Commercially available amylose is fed into a blender concurrently with water at the rate of parts of amylose to 125 parts of a mixture of water and dimethylacetarnide (7:4) and held at a temperature of 60-70" C. for 3 minutes. A further holding time after thoroughly blending the amylose in the aqueous mixture of 12 minutes at a temperature maintained C. is employed. The aqueous slurry from the holding tanks is precipitated with glacial acetic acid and separated from the aqueous medium by filtration and washed two times with glacial acetic acid. Amylose acetate prepared from this activated amylose by reaction with acetic anhydride employing sulfuric acid as catalyst gave a yield 93% amylose acetic having a degree of substitution of 2.96. The product yields good films.

Example 5 Commercially available amylose is fed into a blender concurrently at the rate of parts of amylose to 100 parts of a mixture of water and dimethylacetamide (6:4 ratio) at 94 C. The holding time after thoroughly blending the amylose in the aqueous mixture is 20 minutes at temperature maintained 8090 C. The aqueous slurry from the holding tanks is fed into a methanol precipitating bath and thoroughly mixed. Holding time in the methanol bath is 2 minutes. Where the solid portion of the amylose is precipitated, the amylose from the precipitation step is separated from the aqueous medium by filtration, washed once with methanol, once with glacial acetic acid and given a final wash with glacial acetic acid. Amylose acetate is readily prepared from this treated amylose by a conventional procedure. Upon reaction with acetic anhydride with sulfuric acid as catalyst, the yield 96% amylose acetate having a degree of substitution of 2.87 is obtained. The product dissolved in chloroform when cast on glass plate yields films of good strength and clarity.

Example 6 Commercial amylose is fed into a blender concurrently with water C.) at the rate of 20 parts of amylose to 200 parts of water. The holding time after thoroughly blending the amylose in water is 2 hours. The aqueous slurry from the holding tanks is fed into a propionic acid precipiating bath and thoroughly mixed. Holding time in the acid bath is 2 minutes. The amylose from the precipitation step is separated from the aqueous medium by filtration and washed three times with propionic acid. Amylose propionate is prepared from the thus treated amylose by reacting the activated amylose with propionic anhydride using sulfuric acid as catalyst. A yield of 91% amylose propionate having a degree of substitution of 2.7 is obtained. Flms prepared from a solution thereof cast on a stainless steel belt were clear and had an average tensile strength of 5000 p.s.i.

Example 7 Commercial amylose is fed into a blender concurrently with water C.) at the rate of 20 parts of amylose to 100 parts of water. The holding time after thoroughly blending the amylose in water is 20 minutes at temperature maintained 70-75 C. The aqueous slurry from the holding tanks is fed into a methanol precipitating bath and thoroughly mixed. Holding time in the methanol precipitating bath is 2 minutes. The amylose from the precipitation step is separated from the aqueous medium by filtration, washed once with methanol and twice with butyric acid. Amylose butyrate is readily prepared from the thus treated amylose by reaction of the activiated amylose with butyric anhydride using sulfuric acid as catalyst. A yield 90% amylose butyrate having a degree of substitution 2.4 is obtained. The product forms suitable molded articles.

Example 8 (Comparative) Commercial amylose is fed into a blender concurrently with methanol (25 C.) at the rate of 40 parts of amylose to 200 parts of methanol. The holding time after thoroughly blending the amylose in methanol is 2 hours. The slurry from the holding tanks is separated from the methanol medium by filtration, washed once with methanol and three times With glacial acetic acid. In an effort to prepare amylose acetate from the thus treated amylose by the conventional procedure of reacting with acetic anhydride in the presence of sulfuric acid as catalyst, a relatively unattractive amylose acetate product having a D8 of 0.73 and a yield of 76.5% is obtained. This run illustrates the necessity of aqueous activating medium. Methanol is not a good activating medium.

Example 9 (Comparative) Commercially available amylose is fed into a blender concurrently at the rate of 40 parts of amylose to 200 parts of glacial acetic acid at 25 C. The holding time after thoroughly blending the amylose in the acid is 2 hours. The slurry from the holding tanks is separated from the medium by filtration, washed with glacial acetic acid. Amylose acetate prepared from the thus treated amylose by the conventional procedure of reacting it with acetic anhydride in the presence of sulfuric acid as catalyst gave a yield of 69% amylose acetate having a degree of substitution of 0.74. The necessity of Water as the activating medium is apparent in this run also.

Example 10 (Comparative) Commercially available amylose is fed into a blender concurrently with water (25 C.) at the rate of 40 parts of amylose to 250 parts of water. The holding time after thoroughly blending the amylose in water is 24 hours. The amylose is separated from the aqueous medium by centrifugation and Washed four times with glacial acetic acid. Amylose acetate prepared from the thus treated amylose by reaction with acetic anhydride using sulfuric acid as catalyst gave a yield 97% amylose acetate having a degree of substitution of 2.85. However, due to the long contact period with water the amylose product suffers from substantial deterioration. Deterioration in amylose is found following immersion in Water for periods in excess of about '68 hours. As a consequence it is advantageous that activation by procedures requiring shorter contact periods be employed.

Intrinsic viscosity measurements on this activate-d product show a substantial decrease in molecular weight relative to the activated produce prepared in Example 3 wherein an aqueous activation period of two hours is employed.

Amylose derivatives prepared from the activated amylose according to the invention may usefully be employed as film forming composition, as molding compositions, fiber forming material, in protective coatings, adhesives and the like.

In the use of amylose derivatives, various additives may be introduced into compositions thereof as is known in the art. For example, suitable quantities of plasticizer e.g. dibutyl phthalate may be incorporated in the formation of films.

In the practice of the invention, it is possible to replace up to about 10 to 35% or more of the amylose with amylopectin without substantially impairing the character of the derivative obtained.

We claim:

1. The method for activating retrograded amylose comprising partially swelling the amylose in an aqueous medium in a period not exceeding 4 hours, separating the solid amylose from the liquid phase, Washing said amylose with a non-aqueous liquid which is a non-solvent I for the amylose and separating the non-aqueous liquid.

from the amylose-liquidmixturer'toprovide an amylose product of at least:30% solids. 1

2. The. method for activatingret'rogreded amylose comprising partially swelling'the amylose in an aqueous medium at a temperature between about 80 C. and 100 C. in a period not exceeding about 30 minutes, separating thesolid amylose fromthe liquid phase, Washiug said amylosewith a nonaqueous liquid which is a non-solvent for the amylose and separating sufiicient liquid from theiamylose mixture to provide an amylose productof at1least'30% solids.

3. The method for activating retrograded amylose comprisingpartially swelling the amylose in an aqueous i is ,a-non-solventtor. amylose, fseparating. the: solid, amylose.

from the liquid v.phase washi'ng said amylosewith a nonaqueous non-solvent liquid and separating suflicient liquid from the amylose-liquidmixture to provide ,a product of atleast30% solids;'

8 A continuouswmethod for-activating retrograded amy lose comprising introduc'ing; amylose 'and 'water into a;

. mixing; apparatus; partially swelling'theaamylose in' the mediumat room temperature in a period between l and 3 hours, separatingthe solid amylose from the liquid phase, washing said amylose with. a non-aqueous liquid which aqueousymedium. in aperiod, not exceeding; 4% hours, precipitating; the swollen} amylose. with ;a liquid organic: compound which ismisciblei with said solventiliquid but which is-a non-solvent for amylose by'feeding the swollen. amylose" aqueous slurry-{into a:- hath of; said: organic pre-- cipitatiugliquid, separating the,solid amylose from the" liquid phase, washing said-amylose, with a: non-aqueous non-solvent liquid and.;separatingsuflicien'tdiquid from: the amylose-liquid mixture:to; provide a product" of at,

least% solids;

is a non-solventfor the amylose and separating sufiicienh liquid from the amylose-liquid" mixture to provide an amylose productof at least 30% solids.

4. A continuous method for activating retrogradedfl' amylose comprising introducing amylose andwater into a mixing apparatus, under continuous agitation partially swelling the, amylose in the aqueous medium in a period notexceeding 4hours, separating the solid amylose from a the liquid phase, washing said amylose with a non-aqueous liquid which is a non-solvent for amylose and separating sufiicient liquidfrom the amylose-liquid mixture to provide an amylose product of at least 30=%rsolids.

5. The method for activating retrograded amylose com- I prising partially swelling the amylose. in an aqueous ,medium in a period'not exceeding 4 hours, precipitating the swollen amylose with a.1iquid organic compound which is miscible with water but whichis a non-solvent for amylose, separating the solid. amylose from the liquid phase, washin'gsaid amylose with a non-aqueous non-solvent liquid 1 and separating suflicient' liquid from the amylose-liquid mixture to provide a productof at least 30% solids.

' 6. The method for activating retrograded amylose comprising partially swelling the amylose inan aqueous medium at a'temperaturebetween about 80 C. andl'OO C. in a periodnot' eXceeding about30'minutes, precipitating the swollen amylose with a liquid organic compound" which ismiscible with waterbut which is a non-solvent for amylose, separating the solid amylose from th'e'liquid phase, washing said amylose with a non-aqueous non solvent liquid and separating sufficient liquid from .the. amylose-liquid mixture to provide aproduct of at, least 30% solids.

7. The methodfor activating retrograded amylose coinprising-partially swelling the amylosein an aqueous medium at, room temperature in a period'between' 1 and 3 hours, precipitating the swollen amylose witha liquid, organic compound which is miscible with'water but which I tureto provide a produ'ct'oiiv atleast 30% solids;

#1958, pp."20'6-209:, QMORRIISJO. woLK; Primary Examiner.

V 10; The methodofclaim 5' in which-the amylose is, precipitated with methanol.- U 1 1'1.1The.method of. claim 5, in which the amylose is precipitated with glacia'hacetic acid." j l 12; The method-of claimj' in which the, amylose is precipitatedwithpropi-onicfacidl l3. Thermethod of. claim. 5 in ,whichthe amylose is precipitated withbutyric acid;

References Cited by the Examiner UNITED' STATES PATENTS 2,689,848,} 9/ 54 Hu'semanni'et all; 260-234. 2,779,694 17 5 7 Rascu. 61; all I; 127-71 2,803,568 8757, Bus et.all; l "7-..... 127'71 1 2,853,485 9/758). Werner. et al.f..' 260234..

7 OTHER; REFERENCES 7 Foster" et al':: Journal of Polymer Science, vol; 21", pp.. 91-191 (-1956). y

j Kaplanz- CerealScienceTodayj? vol; 3; No. 8, October ABRAHAM WINKEI'QSTEIN; Examine 

1. THE METHOD FOR ACTIVATING RETROGRADED AMYLOSE COMPRISING PARTIALLY SWELLING THE AMYLOSE IN AN AQUEOUS MEDIUM IN A PERIOD NOT EXCEEDING 4 HOURS, SEPARATING THE SOLID AMYLOSE FROM THE LIQUID PHASE, WASHING SAID AMYLOSE WITH A NON-AQUIOUS LIQUID WHICH IS NON-SOLVENT FOR THE AMYLOSE AND SEPARATING THE NON-AQUEOUS LIQUID FROM THE AMYLOSE-LIQUID MIXTURE TO PROVIDE AN AMYLOSE PRODUCT OF AT LEAST 30% SOLIDS. 